Extremely cold weather imposes severe difficulties upon the starting of an airplane's or automobile's engine. First, the coldness drastically increases the viscosity of the engine's lubricating oil. This includes, in particular, the oil forming a film between the parts of the engine that move relative to each other. Rather than lubricating the relative motion of these parts, the cold viscuous oil tends to act as a glue between them.
Second, the low temperatures severely limits the rate of the chemical reactions taking place in the vehicle's battery which provide its electrical energy. Consequently, even a properly charged battery can provide substantially less power than it can at warmer temperatures.
Thus, because of the cold weather, the battery provides the starter motor with less than its normal power for cranking the engine to commence the combustion processes. The cold weather further impedes this process by causing the oil to further inhibit the engine's motion.
Airplane engines, because of their critical construction, specifically require warming prior to starting should the ambient temperature fall below a predetermined level. Typically, the engine manufacturers specifically state that such warming precede attempts to start below 10.degree. F. Automobile engines, on the other hand, do not have such specific requirements. However, at extremely cold temperatures, the difficulty incurred in starting them may prove insurmountable without such prewarming.
Various devices have found use in the warming of engines prior to their starting on cold days. U.S. Pat. Nos. 2,078,116 to E. J. Arndt, 2,418,097 to A. P. Ruff, and 3,233,077 to L. E. Miller all disclose engine heaters for airplanes. Miller in particular utilizes the electrical energy from the airplane's battery to operate his device. He inverts the d.c. current from the battery to an a.c. potential which then transforms to a potential for igniting the fuel in the heater. Miller, on the other hand, simply utilizes the usual a.c. potential at an outlet to light an electrical bulb and drive a fan to heat the motor.
U.S. Pat. Nos. 2,535,758 to O. R. Schoenrock, 3,131,864 to M. Young, 3,234,928 to L. H. Smith, 3,400,700 to S. B. Lindsey et al., and 4,010,725 to C. G. White all show engine heaters utilizing the current of a battery to control the production of the desired heat. Edlund et al., in their U.S. Pat. No. 3,870,855, show an engine heater using alternating current to both produce and control the heat required to prewarm the engine. It also rectifies a portion of this a.c. to provide a d.c. to charge the vehicle's battery.
However, each of the systems described above for prewarming engines require the availability of a particular type of electrical energy. The absence of the required source, or its presence in insufficient amounts, will preclude the engine warmer from performing its required tasks.
The device of Edlund et al. can only function when connected to the usual source of house current. However, in the absence of an outlet for such electricity, which frequently occurs around automobiles and airplanes, the device does not prepare the engine for starting. The other devices require stored energy from a battery. However, the battery may not have sufficient power to operate the warmers. In either case, the device suffers serious shortcomings that limit its utility when required.